组合模式

描述

组合模式,又叫部分整体模式,用于把一组相似的对象按照对象关系组合为一个单一对象,其依据树形结构来组合对象。

光说概念太难理解了,举个例子,有个员工类(Employee),那么一个公司的所有人都可以用这个类的对象来表示,因为不管是首席执行官(CEO)、销售主管(headSales)、营销主管(headMarketing)或者普通的使用者(tester)和开发人员(programmer)都是员工类的具体对象,并且他们是有树形关系的,其关系如下:

那么此时,就可以把这七个相似对象组合为一个简单对象了,访问时候通过树形结构的特点来访问就可以了。

使用场景:当系统中的对象关联为树形,有层次结构时可以使用,这时候可以忽略单个对象的不同

实例

import java.util.ArrayList;
import java.util.List;

class Employee {
   private String name;
   private String title;
   private List<Employee> subordinates;

   public Employee(String name,String title) {
      this.name = name;
      this.title = title;
      subordinates = new ArrayList<Employee>();
   }

   public void add(Employee e) {
      subordinates.add(e);
   }

   public void remove(Employee e) {
      subordinates.remove(e);
   }

   public List<Employee> getSubordinates(){
     return subordinates;
   }

   public String toString(){
      return "Employee :[ Name : "+ name 
      +", dept : "+ title +subordinates +" ]";
   }   
}

public class Main {
   public static void main(String[] args) {
      Employee CEO = new Employee("John","CEO");

      Employee headSales = new Employee("Rob","Sales");

      Employee headMarketing = new Employee("Mike","Marketing");

      Employee programmer1 = new Employee("Lili","Programmer");
      Employee programmer2 = new Employee("Bob","Programmer");

      Employee tester1 = new Employee("Jack","Tester");
      Employee tester2 = new Employee("Tom","Tester");

      CEO.add(headSales);
      CEO.add(headMarketing);

      headSales.add(tester1);
      headSales.add(tester2);

      headMarketing.add(programmer1);
      headMarketing.add(programmer2);

      //print all employees of the organization
      System.out.println(CEO); 
      for (Employee headEmployee : CEO.getSubordinates()) {
         System.out.println(headEmployee);
         for (Employee employee : headEmployee.getSubordinates()) {
            System.out.println(employee);
         }
      }    
   }
}

运行结果如下:

 

代码来源:特别感谢 w3School提供的代码和解释

 

posted @ 2017-11-27 11:07  K_artorias  阅读(199)  评论(0编辑  收藏  举报